# AD 48-26-01: Engine Speed Restrictions-Curtiss Prop

- Type: Airworthiness directive
- Status: Current
- Products: Lockheed 649-79 and 749-79
- Superseded by: Nothing supersedes this AD
- Product type: Aircraft, Large airplane
- Registered aircraft: 1 may be affected, by airframe or engine model (OpenAirDocs)
- FAA DRS: https://drs.faa.gov/browse/excelExternalWindow/303E939EABAAC0848625696D0071A51C.0001
- DRS record last changed: May 30, 2024
- Page: https://openairdocs.org/ad/48-26-01

## The airworthiness directive

48-26-01 LOCKHEED: Applies to 649 and 749 Series Aircraft Equipped With Curtiss C632S-A14/850-4C2-0 Propellers.

Compliance required by July 7, 1948, and August 1, 1948.

To avoid failures under certain operating conditions, the following engine speed restrictions must be observed and two placards covering these restrictions must be installed in the cockpit. (Temporary placards must be installed not later than July 8, 1948, and permanent placards to be supplied by Lockheed installed not later than August 1, 1948.) One placard must be in full view of the pilots and one in full view of the flight engineer. Placards should read as follows:

"In flight avoid continuous operation below 1,625 r.p.m. and between 1,725 and 1,850 r.p.m., 1,900 and 2,000 r.p.m., and between 2,100 and 2,375 r.p.m. On ground avoid continuous operation between 1,200 and 1,450 r.p.m." For visual reference, all tachometers in the airplane must be marked as follows not later than August 1, 1948: "Red Band1,200 to 1,625 r.p.m. Green band 1,625 to 1,725 r.p.m. with green radial line at 1,675 r.p.m. Red band 1,725 to 1,850 r.p.m. with green radial line at 1,875 r.p.m. Red band 1,900 to 2,000 r.p.m. Green band 2,000 to 2,100 r.p.m. with green radial line at 2,050 r.p.m. Red band 2,100 to 2,375 r.p.m. with green radial line at 2,400 r.p.m. Yellow band 2,400 to 2,800 r.p.m. with red radial line at 2,800 r.p.m."

## Affected data sheets (1) (OpenAirDocs)

The type certificate data sheets whose models the AD names.

- [TCDS A-763](https://openairdocs.org/tcds/A-763): Lockheed Martin Aeronautics Company; names 2 of 6 models: 649-79, 749-79

## Registered aircraft it may apply to (OpenAirDocs)

Matched by airframe and engine model; the AD's applicability may narrow it by serial number, part number or equipment.

- Aircraft: 1 (1 by airframe model, 0 by engine model)
- Makers: Lockheed 1

Models with the most aircraft:

- [Lockheed 749-79](https://openairdocs.org/model/lockheed-749-79): 1 aircraft (airframe model)

All 1 models: https://openairdocs.org/ad/48-26-01/models.md
Every aircraft: https://openairdocs.org/ad/48-26-01/aircraft.md

Its text cites no advisory circulars or STCs.

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